1. Field of the Invention
The present invention relates to color processing for estimating an output color of a printing device.
2. Description of the Related Art
As an estimation method of a color to be reproduced by a printer, a Cellular Yule-Nielsen Neugebauer model is known. With this model, color patches corresponding to grid points set in advance are printed by the printer, and a color (output color) to be reproduced by the printer with respect to an arbitrary input value is estimated according to the Neugebauer model based on color information obtained by measuring the color patches. However, because a limitation of the total amount of applied color materials such as inks is often exceeded, the color patches of not all grid points set in advance can be printed. Hence, in Y. Chen, R. S. Berns and L. A. Taplin, “Six Color Printer Characterization Using an Optimized Cellular Yule-Nielsen Spectral Neugebauer Model”, J. Imaging Sci. Tech. Vol. 48, No. 6, pp. 519-528 (2004), color information of grid points which cannot be printed is estimated by multiple regression from that of the printed and measured color patches.
With the estimation method of the above reference, the number of color patches to be printed and measured becomes huge if the number of color materials increases. In order to improve color estimation precision, the number of grid points needs to be increased. However, it is not practical to print and measure a huge number of color patches. For this reason, grid points which are not printed and measured become constraints, and sufficiently high precision cannot be obtained.
Also, print sheets of different types used in printing have different limitations as to the total amount of applied color materials. Hence, the number of color patches to be printed varies depending on the types of print sheets, thus readily introducing confusion upon printing and measurement of the color patches.
The aforementioned problems pose a serious bottleneck along with the current progress of multi-color printers.